Global distribution systems, such as the Internet, are increasingly being used for distribution of digital content that includes text and graphic information encoded in a variety of formats. However, copyright holders and publishers of such digital content have been slow to embrace the use of the Internet for distribution of digital content because it has been difficult to control unauthorized copying and dissemination of the content once it has been delivered onto the Internet. In particular, once content has been placed in digital form and delivered to a user, it can easily be copied, printed or forwarded to other users.
Thus, providers of digital content desire to establish a secure, global distribution system for digital content that protects the rights of the content's copyright holders. One prior art technique for controlling the distribution of digital content is shown in FIG. 1. In this technique, unencrypted content is placed in a server farm that is located behind a secure firewall. A user, such as user 100 desiring access to the content stored in database 106 logs in to the server 104 using a conventional authentication scheme, such as a password or subscription service. Once connected to the server 104, an authorized user 100 can view content and request a copy of that content as indicated by arrow 108. In response to this request, the server 104 retrieves the information from the database 104 as indicated schematically by arrow 110 and displays the content.
This conventional protection technique has several drawbacks. First, many users prefer to view the content with a conventional web browser. In order to display the content in such a browser, it is necessary to download a digital version of the content, as indicated schematically by arrow 112. This digital version is typically stored, at least temporarily, in the computer, and can be printed or forwarded to other users. Therefore, in accordance with another prior art technique, in order to view the content, the conventional browser must be equipped with a plug-in, ActiveX components or another program which controls the browser and disables the printing function and prevents forwarding the content to unauthorized users. However, in order to use this system, it is necessary to first download and install the plug-in, the ActiveX libraries or other program, before the content can be viewed. In addition, since the content is not encrypted when it is downloaded to the browser, it can still be stored and then later printed or forwarded to other users.
Another problem with this conventional system is that the content sits behind a firewall and it is not directly accessible from the Internet. Consequently, the content cannot be easily cataloged and indexed by conventional search tools, such as search engines or web crawlers. This cuts off a source of potential revenue for the content provider from users who might be interested in the material if they were made aware of it. In addition, locating the content behind a firewall forces authorized users to log in to the server before they can conduct a search for selected material.
Another conventional protection technique is called a “secure container” system. In this system, the content is delivered to the user in an encrypted form and is decrypted at the user's site by means of a decryption key. This technique provides a solution to protecting the document during delivery over insecure channels, but has the same drawback as the firewall system in that the encrypted content cannot be easily cataloged and indexed by conventional search tools.